This invention relates to a composition derived from a softening agent for rubber and a thermoplastic resin composition containing the same.
Conventionally, a thermoplastic elastomeric resin composition having a desired hardness has been produced by adding oils as a plasticizer and olefinic resins as a resin component to a styrenic resin composition or an ethylene-propylene resin composition (see, for example, Japanese Patent Application Laid-Open Nos. S54-99156, S58-145751, S61-28548, H05-287132 and H08-66990). As the oils, paraffin oil has been often used. However, although the addition of the oils makes the hardness lower, it causes deterioration in heat resistance, weathering resistance, mechanical strength, and abrasion resistance because the molecular weights of the oils used are lower than those of the resin components.
If use is made of conventional oils which are not crosslinked to obtain a very soft thermoplastic resin composition, the oils will bleed out onto the surface of a molded article and thus a satisfactory molded thermoplastic resin composition is not attained.
Further, the amount of oils which can be absorbed in a thermoplastic resin composition is limited. A largest ratio of the amount of oils to be absorbed to the amount of a thermoplastic resin composition is just over 3. If the oil is added more than the upper limit, bleed-out of the oil occurs.
The oils are liquid, while the other components are solid. Accordingly, the oils are troublesome to handle and require a special equipment for blending such as a pump.